We have explored the use of green fluorescent protein as a tracer dye for cell movements in developing early zebrafish (Danio rerio) embryos. We study the expression of the homeodomain transcription factor zOtx1 to study the movement of cells that ectopically express this factor. Embryos injected with RNA encoding zOtx1 appear to have gastrulation defects indicative of abnormal cell movements. Co-injection of GFP and zOtx1 RNAs into single cells at the 16 cell stage yields bright fluorescence that can be detected in a subpopulation (about 5-10%) of cells in the 5 hour blastula. We will study the lineage and movement of these labeled cells in order to elucidate the possible role of zOtx1 in restriction of cell movements and promotion of cell adhesion. 8-31-96